The present invention relates to angle measurement systems (AMS) of the type using a polygonal body, which is externally attached to a workpiece or other object whose accurate angular displacement is to be determined, and an optical device adapted to translate the angular displacement of the polygon into a readable measurement, preferably relative to a predetermined reference or zero position.
In more detail, it has already been proposed to provide an AMS, such as schematically represented in FIG. 1, comprising a regular polygon P with n planar, light reflecting facets A1, A2, A3, . . . , An, extending in planes which form angles a1, a2, a3, . . . , an therebetween; an autocollimator C or similar beam deflection analyzing and transducing device; and a measuring device M, with analog or digital display represented (for the sake of illustration only) by scale S and pinhole or reticle R, indicating the deviation of the reflected light beam from the head-on or "O" position in either one (+a) or the other (-a) rotated directions of the reflective polygon facet A1.
One of the major deficiencies of such a measuring method and system is the strict requirement that all the angles a be equal to each other to an extremely high degree of precision; otherwise, when passing from one facet to the other (or taking a measurement of an angle greater than a and up to 360.degree.), the error (e.g., (a1-a2), or (a1-a3), etc.) in the output measurement will be noticeable, thereby resulting in an incorrect reading.
For this reason, polygons suitable for use in this type of AMS are prohibitively expensive (on the order of a few thousands of Dollars).